Portable computers such as laptops, notebooks, subnotebooks and so forth (referred to herein generally as laptop computers) today utilize as system processors integrated circuit chips that can be cooled by natural convection or by included forced air cooling systems. Natural convection adequately cools "low-to-mid-power" microprocessor chips, while the included forced air cooling systems cool "mid-to-high-power" microprocessor chips. The forced air cooling systems use relatively small, and relatively quiet, fans that are readily incorporated into the laptop computers.
The next generations of microprocessors which manufacturers are contemplating using in laptop computers are higher power, higher density circuits. Moreover, these processors operate at higher speeds. They thus dissipate substantially more heat than the prior mid-power circuits. Accordingly, they can no longer be adequately cooled by the forced air cooling systems currently used to cool these computers. Forced air cooling systems that could potentially cool these high-power circuits are too large, too heavy, consume too much battery power and/or are too noisy for the laptop computers. These processors instead require their own, i.e., dedicated, cooling systems.
One type of dedicated cooling system uses a liquid coolant that changes phase as it absorbs heat. That is, the coolant changes from a liquid to a vapor as heat is transferred from the circuit to the coolant. It then changes from a vapor to a liquid as it transfers the heat to a cooler surface. Such systems are commonly referred to as two-phase systems.
The coolant in a two-phase system may be housed in a conventional heat pipe, which is a rigid tube with one end acting as an evaporator and the other end acting as a condenser. The end of the pipe which acts as the evaporator is placed in contact with the circuit and conducts heat, through its walls, from the circuit to the coolant. When sufficient heat has been transferred to the coolant, the coolant vaporizes and the vapor travels through the pipe to the condenser, where it dissipates heat and changes back to a liquid. A wick or other capillary device may be included to draw the liquid coolant back through the pipe to the evaporator.
Such conventional two-phase cooling systems generally work well. However, they take up a relatively large amount of space. If the device in which the cooling system is installed is a workstation, for example, the device has sufficient room to house a conventional two-phase cooling system that has a condenser which is large enough to cool a high power, high density processor. If, however, the device is a laptop computer, it may not have enough room for the components of such a two-phase system, and, in particular, it may not have room for the condenser. Further, as designers of the laptop computers endeavor to make newer models even more compact, and thus, easier to transport and handle, they reduce further the space allotted to the cooling system.
Laptop computers generally do not have the high quality screens that are now common on personal computers. These high quality screens require high power screen drivers, which must be adequately cooled to operate properly. Accordingly, what is needed is a cooling mechanism that fits within the confines of a laptop computer and can dissipate the heat produced by high power screen drivers, as well as the high power system processors, included therein.